Chapter 5: Variations in Consciousness
The Nature Of Consciousness
Consciousness is the awareness of internal and external stimuli.
• we seem to maintain some degree of awareness even when we are asleep, and sometimes even when we
are under anesthesia for surgery.
1. Variations in Awareness and Control.
• some of what enters our consciousness seems intentional, other thoughts seem to just meander into our
Mind wandering refers to people’s experience of task-unrelated thoughts, thoughts that are not related to
what they are intentionally trying to do at a given moment.
• mind wandering is less likely to occur if the task you are engaged in is one that requires signiﬁcant
Controlled processes- judgements or thoughts that we exert some control over, that we intend to occur.
Automatic processes- happen without our intentional control or eﬀort.
2. Consciousness and Brain Activity.
• consciousness arises from activity in distributed networks of neural pathways.
• one of the best physiological indicators of variations in consciousness is the EEG.
• diﬀerent patterns of EEG are associated with diﬀerent states of consciousness:
EEG Pattern Frequency (cps) Typical States of Consciousness
Beta (β) 13-24 Normal walking thought, alert problem solving;
Alpha (α) 8-12 Deep relaxation, blank mind, meditation;
Theta (θ) 4-7 Light sleep
Less than 4 Deep sleep
Biological Rhythms and Sleep
Biological rhythms are periodic ﬂuctuations in physiological functioning. • the existence of these rhythms means that organisms have internal “biological clocks” that somehow
monitor the passage of time.
1. The Role of Circadian Rhythms.
Circadian rhythms are the 24-hour biological cycles found in humans and many other species.
• in humans, circadian rhythms are particularly inﬂuential in the regulation of sleep.
• research indicates that people generally fall asleep as their body temperature begins to drop and awaken as
it begins to ascend.
each individual may have an “ideal” time for going to bed, which promotes better quality of sleep during
• circadian rhythms generally persist when external time cues are eliminated.
• when exposed to light, some receptors in the retina send direct inputs to a small structure in the
hypothalamus called the suprachiasmatic nucleus (SCN).
the SCN sends signals to the nearby pineal gland,whose secretion of the hormone melatonin plays a key
role in adjusting biological clocks.
2. Ignoring Circadian Rhythms.
if you get less than the amount of sleep that you need, you accumulate “sleep debt.”
• getting out of sync with your circadian rhythms causes jet lag. When you ﬂy across several time zones, your
biological clock keeps time as usual, even though oﬃcial clock time changes.
• chronic jet lag appears to be associated with measurable deﬁcits in cognitive performance.
• people diﬀer in how quickly they can reset their biological clocks to compensate for jet lag.
3. Melatonin and Circadian Rhythms.
• melatonin regulates the human biological clock.
• it can reduce the eﬀects of jet lag by helping travelers resynchronize their biological clocks.
The Sleep and Waking Cycle
• sleepers experience quite a bit of physical and mental activity throughout the night.
• in addition to an EEG, other 2 crucial devices are an electromyograph(EMG), which records muscular
activity and tension, and an electrooculograph(EOG), which records eye movement. Other instruments
are also used to monitor heart rate, breathing, pulse rate, and body temperature.
1. Cycling through the Stages of Sleep.
during sleep, people cycle through a series of 5 stages.
• a) Stages 1-4:
• there is no obvious transition point b/w wakefulness and sleep.
it’s a brief transitional stage of light sleep that usually lasts only a few (1-7) min.
• breathing and heart rate slow as muscle tension and body temperature decline.
• theta waves are prominent in EEG activity.
• hypnic jerks - brief muscular contractions that occur as people fall asleep- occur during this stage.
• it lasts about 10-25 min
• during this stage, brief bursts of higher-frequency brain waves, called sleep spindles, appear agains a
background of EEG activity.
• respiration rate, heart rate, muscle tension, and body temperature continue to decline.
STAGES 3 & 4
Slow-wave sleep (SWS) consists of sleep stages 3 and 4, during which high-amplitude, low-frequency
delta waves become prominent in EEG recordings.
• individuals reach SWS in about an hour and stay there for roughly 30 min.
the cycle reverses itself and the sleeper gradually moves back upward through the lighter stages.
b) REM Sleep:
REM sleep is a relatively deep stage of sleep marked by rapid eye movements; high-frequency, low-
amplitude brain waves; and vivid dreaming.
when sleepers reach stage 1 once again, they usually go into the 5th stage of sleep-REM(rapid eye
• REM sleep was discovered accidentally in the 1950s by grad student William Dement.
• this stage tends to be a “deep” stage of sleep-people are relatively hard to awaken from it.
• it’s also marked by irregular breathing and pulse rate.
muscle tone is extremely relaxed-so much so that body movements are minimal and the sleeper is visually
✴Although REM is relatively deep stage of sleep, EEG activity is dominated by high-frequency beta waves
that resemble those observed when people are alert and awake.
• this paradox is probably related to the association b/w REM sleep and dreaming.
most dream reports come from the REM stage.
• dreams in REM stage are more frequent, vivid, and memorable than dreams experienced in the other 4
• diﬀerent stages of sleep may be implicated in memory for diﬀerent types of tasks or information.
c) Repeating the Cycle:
• during the course of a night, people usually repeat the sleep cycle about 4 times. • the ﬁrst REM period is relatively short, lasting only a few minutes. Subsequent REM periods get
progressively longer, peaking at around 40-60 min.
• NREM intervals tend to get shorter.
2. Age Trends in Sleep.
• age alters the sleep cycle
• babies only have 2 sleep types: REM and non-REM sleep.
• during adulthood, the proportion of REM sleep remains stable, however, the percentage of slow-wave
sleep declines dramatically and the percentage of time spent in stage 1 increases slightly, with trends
stronger in men than in women.
• the average amount of total sleep time also declines with advancing age.
3. Culture and Sleep.
• the physiological and psychological experiences of sleep does not appear to vary systematically across
• cultural disparities in sleep are limited to more peripheral matters, such as sleeping arrangements and
4. The Neural Bases of Sleep.
• sleep depends on the interplay of many neural centres and neurotransmitters.
• the rhythm of sleep and waking appears to be regulated by subcortical structures that lie deep within the
• reticular formation plays an important part in the regulation of sleep and wakefulness.
The ascending reticular activating system (ARAS) consists of the aﬀerent ﬁbres running through the
reticular formation that inﬂuence physiological arousal.
• the ARAS projects diﬀusely into many ares of the cortex.
when these ﬁbres are cut in the brainstem of a cat, the result is continuous sleep.
• many other brain structures are involved as well:
- the pons and adjacent areas in the midbrain seem to be critical to the generation of REM sleep.
- speciﬁc ares in the medulla,thalamus,hypothalamus, and limbic system have also been implicated in the
control of sleep and waking.
the neurotransmitters serotonin and GABA appear to play especially important roles in the regulation of
sleep, however, other neurotransmitters such as norepinephrine,dopamine, and acetylcholine inﬂuence the
course of sleep and arousal as well.
5. Doing Without: Sleep Deprivation.
a) Sleep Restriction: • partial sleep deprivation, or sleep restriction, occurs when people make do with substantially less sleep
than normal over a period of time.
• eﬀects depend on the amount of sleep lost and on the nature of the task at hand.
• negative eﬀects are most likely when subjects are asked to work on long-lasting, diﬃcult tasks, or when
they are asked to restrict their sleep to less than 5 hours from many nights.
b) Selective Deprivation:
• the eﬀects of REM deprivation has a little impact on daytime functioning and task performance, but it
does have some interesting eﬀects on subjects’ pattern of sleeping.
as the nights go by in REM-deprivation studies, it becomes necessary to awaken the subjects more and
more often to deprive them of their REM sleep, because they spontaneously shift into REM more and
• after the experiment is done and the subjects are allowed to sleep without interruption, they experience a
“rebound eﬀect”- they spend extra time in REM periods for 1 to 3 nights to make up for their REM
• REM and slow-wave sleep contribute to the following:
- learning that takes place during the day
- promoting diﬀerent types of memory
6. Sleep Disorders.
Insomnia refers to the chronic problems in getting adequate sleep.
• it is the most common sleep disorder.
it occurs in 3 basic patterns:
1) diﬃculty in falling asleep
2)diﬃculty in remaining asleep
3)persistent early morning awaking.
• insomnia is associated with daytime fatigue, impaired functioning, in elevated risk of accidents, reduced
productivity, depression, and increased health problems.
• nearly everyone suﬀers occasional sleep diﬃculties because of stress, disruption of biological rhythms, or
other temporary circumstances.
the prevalence of insomnia increases with age and is about 50% more common in women than in men
• some people might suﬀer from “pseudo-insomnia,” or sleep state misperception, which means that they just
think they are getting an inadequate amount of sleep.
• about 5% of insomnia patients show sound patterns of sleep.
• it has many causes • it is often a side eﬀect of emotional problems, such as depression, or of signiﬁcant stress, such as pressures
• health problems such as back pain, ulcers, and asthma can lead to insomnia.
• the use of certain drugs, such as cocaine, may also lead to insomnia.
• the most common approach is the prescription of sedative drugs.
• benzodiazepine medications, which exert their eﬀects at GABA synapses, are the most widely prescribed
prescription of sleeping pills have declined signiﬁcantly in recent decades
• sedatives can be a poor long-term solution for insomnia for a number of reasons:
- they have carryover eﬀects that can make people drowsy on the next day
- they can also lead to memory decrements
- they can cause an overdose in combination with alcohol or opiate drugs.
- people can become physically dependent on sedatives
- with continuous use, sedatives become less eﬀective
- most of them interfere with the normal cycle of sleep
• newer sedatives such as zolpidem reduce some of the problems associated with traditional sleeping pills.
• melatonin can also be used for treatment.
relaxation procedures and behavioural interventions can be helpful for many individuals.
b) Other sleep disorders:
Narcolepsy is a disease marked by sudden and irresistible onsets of sleep during normal waking periods.
- a person suﬀering from narcolepsy goes directly from wakefulness into REM sleep, usually for a short
period of time (10-20 min).
- this is a potentially dangerous condition since some victims fall asleep instantly.
- its causes are not well understood, but some people tend to be genetically predisposed to it.
- stimulant drugs have been used to treat this disorder
Sleep apnea involves frequent, reﬂexive gasping for air that awakens a person and disrupts sleep.
- it occurs when a person stops breathing for a minimum of 10 sec.
- heart failure is prevalent among people with some speciﬁc types of sleep apnea.
- it is usually accompanied by loud snoring
- it often leads to insomnia as a side eﬀect
Nightmares are anxiety-arousing dreams that lead to awakening, usually from REM sleep.
- a person who awakens from nightmares may have diﬃculty getting back to sleep.
- nightmares are most common in children.
- persistent nightmares may reﬂect an emotional disturbance. Night terrors are abrupt awakenings from NREM sleep, accompanied by intense autonomic arousal and
feelings of panic.
- they happen during stage #4
- they produce remarkable accelerations of heart rate
- victims usually let out a p